Tearable core member and cold-shrink tube device having the same

ABSTRACT

In a cold-shrink tube device, to permit a core member to be readily and correctly removed from an elastic tube member without deteriorating an attaching operability onto an object wherein the core member holds an end region of an elastic tube member in an elastically expanded condition. A hollow tubular body of the core member is torn into a ribbon shape along a weakened line formed spirally and continuously over an entire axial length of the body. A ribbon-shaped region defined in a spiral on the body by the weakened line includes a major ribbon section having an axial dimension larger than an axial dimension of an end ribbon section defined, adjacent to a tearing-start end, between the weakened line and one axial end of the body. When the core member is arranged in the end region of the elastic tube member, the ribbon-shaped region of the body with around three coils, including the end ribbon section and the major ribbon section, is accommodated inside the end region.

DETAILED DESCRIPTION OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a tearable core member. Further, thepresent invention relates to a cold-shrink tube device having thetearable core member.

2. Prior Art

A cold-shrink tube device comprising an elastic tubular member having anopen end and a hollow tubular core member removably provided in an areahaving a predetermined length from the open end within the elastic tubemember to hold this area in an elastically expanded state has been usedin various fields as a covering device for quickly attaching to anobject. For example, a cold-shrink type cover tube has been known (see,for example, Japanese Unexamined Patent Publication (Kokai) Nos.3-143217 and 7-57798), which covers an electric wire exposed in aconnected portion between cables (or covered electric wires) or thatbetween the cable and a terminal member of other conductor for thepurpose of moisture-proof, electrical insulation and mechanicalprotection. An elastomer tube having a length exceeding the entirelength of the connected portion is held in advance in an elasticallyexpanded state by a hollow tubular plastic core, which core member isremoved when-the elastomer tubular member is applied to the connectedportion so that the expanded area elastically shrinks.

The core member used in such a kind of cold-shrink tube device generallyhas a groove or weakened line continuously formed in a spiral shape allover the entire length of a hollow tubular body in the axial directionthereof. This core member is capable of tearing the body into a ribbonshape along the groove while using one axial end of the groove as atearing-start end. A method for producing the core member is described,wherein a continuous plastic ribbon having a constant width andthickness all over the entire length is spirally wound and adjacentcoils are bonded together along the lateral edges thereof by the weldingor others so that a cylindrical body is formed having a spiral groovedefined by the bonded portion (see, for example, Japanese UnexaminedPatent Publication (Kokai) No. 10-513337 and International PatentPublication No. WO 99/08355).

Another core member has been also known, wherein the hollow tubular bodyis able to be torn along a cut line or a weakened line continuouslyformed over the entire length in the axial direction thereof whileregularly meandering (see, for example, Japanese Unexamined UtilityModel Publication (Kokai) No. 7-2692). This core member is integrallymolded with resinous material by an injection molding process.

The conventional core member having the spiral or meandering weakenedline of the above-mentioned type is integrally connected at an axial endof the body to the ribbon area formed in the body by the weakened lineso that the extension part extending from the body is further provided.When the core member is disposed within the elastic tubular member, theextension part is inserted in advance into the interior of the body toproject the distal end of the extension part from outside of the otheraxial end of the body. The core member is disposed within the elastictubular member so that the following orientation is made wherein theother axial end of the body and the distal end of the extension part areexposed from the open end of the elastic tubular member.

According to the cold-shrink tube device having the above-mentionedprior art tearable core member, the longer the length of the core memberin the axial direction, the longer the time required for removing thecore member. Particularly, in the core member having the spiral weakenedline, the ribbon-like cutting piece of the body torn by pulling thedistal end of the extension part exposed from the open end of theelastic member tends to entangle with the objective while maintainingthe spiral shape, during the mounting of the cold-shrink tube device tothe objective (for example, the electric wire connected portion). Insuch a case, it is necessary to tear the body while unwinding theentanglement of the ribbon-like cutting piece, resulting in muchconsumption of time and labor for the removal of the core member.

To avoid such inconvenience, the axial-directional distance betweenevery adjacent coil of the weakened line extending in the spiral manneris widened to enlarge the axial-directional dimension or the widthwisedimension of the ribbon area formed on the body by the weakened line. Bydoing so, it is possible to mitigate the degree of entanglement of theribbon-like piece with the objective because the entire length of theribbon-like piece of the torn body becomes shorter.

However, in this case, the extension part inserted into the interior ofthe body of the core member prior to being mounted to the objective iswidened in width in accordance with the enlargement of the widthwisedimension of the ribbon-like area. Since it is largely expanded in theinterior of the body in the vicinity of the integrally connected portionwith the body to narrow the interior space, there is a particularproblem in that it is difficult to smoothly insert the objective intothe cold-shrink tube device. Also, according to the core member made bywinding the continuous ribbon in a spiral manner and integrally bondingthe respective coils, since the rigidity of the core member increases asthe widthwise dimension of the ribbon becomes larger, it is necessary toincrease the mechanical strength of the bonded portion for the purposeof maintaining the cylindrical form of the ribbon. As a result, a largeforce is required for tearing the body, and also there is a risk in thatthe tearing operation becomes unstable due to the variety of themechanical strength in the bonded portion.

Contrary to this, in the core member having the weakened line extendingin a meandering manner described above, the ribbon-like area formed inthe body by the weakened line is extended as it is generally encircledthe body about one or two times. Therefore, if the body is torn bypulling the distal end of the extension part outward, the tearingadvancing direction is reversed at generally one or two times.Accordingly, when the body is torn by pulling the distal end of theextension part, the tearing advancing direction is reversed around theobjective generally at one or two times, and as a result, it is expectedthat the ribbon-shaped cut piece of the body is not of a spiral shapeand is removable from the objective without being entangled with theobjective. According to this arrangement, irrespective of the dimensionof the core member, it is possible to tear the body into a ribbon-shapeand remove the core member from the elastic tubular member. In thisarrangement, however, a stretching force applied to the ribbon-like cutpiece when the body is torn is liable to cause the stress concentrationin the reverse part of the ribbon-like cut portion. As a result, whenthe extension part is particularly vigorously stretched, there is a riskin that the ribbon-like cut piece may be severed at the reverse part. Ifthe ribbon-like cut piece is severed off, it is difficult to remove thecore member from the elastic tubular member, whereby the operation mustbe carried out with a great care which consumes much time and labor forthe removal of core member.

An object of the present invention is to provide a cold-shrink tubedevice having a tearable core member capable of not deteriorating theoperability for mounting the same to the objective and of quickly andaccurately removing the core member from the elastic tubular member.

Another object of the present invention is to provide a tearable coremember usable in a cold-shrink tube device wherein a risk is avoidablein that the ribbon-like cut piece of the torn core body is entangledwith the objective to which the cold-shrink tube device is mounted orcut during the tearing operation to realize the stable tearingoperation.

SUMMARY OF THE INVENTION

The invention of provides a core member comprising a hollow tubular bodyand a weakened line formed to extend spirally and continuously over anentire axial length of the body, the body being able to be torn into aribbon shape along the weakened line from an end of the weakened lineprovided as a tearing-start end at one axial end of the body,characterized in that the weakened line comprises a perforated lineincluding a plurality of joint portions and a plurality of penetratingslits arranged alternately, and extends in a spiral with uneven gapsdefined between adjacent coils in an axial direction of the body; andthat a region of the ribbon shape, defined in a spiral on the body bythe weakened line, includes an end ribbon section defined, adjacent tothe tearing-start end, between the weakened line and the one axial endof the body, and a major ribbon section having an axial dimension largerthan an axial dimension of the end ribbon section.

In one embodiment, the invention provides a core member wherein one ofthe joint portions is formed at the tearing-start end of the weakenedline, and wherein at least the one joint portion, optionally as well asseveral joint portions near the one joint portion when viewing in anextending direction of the weakened line, has a tearing strength largerthan that of remaining joint portions.

The invention may comprise joint portions wherein each of the jointportions of the weakened line includes a pair of outer surfaces mutuallycrossing in an acute angle at a tearing-start side of each jointportion, and may further comprise an extension part connected integrallywith the end ribbon section and extending from the body, a substantiallyannular tab being integrally formed at a distal end of the extensionpart, wherein the body, the extension part and the tab are formed as aone-piece article molded from a resinous material.

The invention also provides a core member comprising a hollow tubularbody and a weakened line formed to extend spirally and continuously overan entire axial length of the body, the body being able to be torn intoa ribbon shape along the weakened line from an end of the weakened lineprovided as a tearing-start end at one axial end of the body,characterized in that the core member comprises an extension partconnected integrally with a region of the ribbon shape, defined in aspiral on the body by the weakened line, at the one axial end of thebody; and that the extension part includes a width dimension smallerthan an axial dimension of the region of the ribbon shape.

The invention further provides a cold-shrink tube device comprising anelastic tube member including an opening end, and a hollow tubular coremember removably arranged inside the elastic tube member in a region ofa predetermined length from the opening end to hold the region in anelastically expanded condition, characterized in that the core membercomprises a core member as set forth in any one of claims 1 to 6.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—A partially broken front view of a cold-shrink tube deviceaccording to one embodiment of the present invention.

FIG. 2—An enlarged front view illustrating a core member disposed in thecold-shrink device shown in FIG. 1.

FIG. 3—A perspective view of the core member of FIG. 2 after beingmolded.

FIG. 4—A front view (a) and a side view (b) of the core member afterbeing molded.

FIG. 5—An enlarged sectional view illustrating a structure of a weakenedline in the core member of FIG. 2.

FIG. 6—(a) to (e) illustrate various modifications of a joint portionprovided in the weakened line of FIG. 5.

FIG. 7—A front view of a modification of a core member.

FIG. 8—A side view of another modification of a core member.

FIG. 9—A front view of a further modification of a core member.

EXPLANATION OF REFERENCE NUMERALS

-   10 . . . cold-shrink tube device-   12 . . . core member-   14 . . . open end-   16 . . . elastic tube member-   18 . . . end region-   22 . . . body 24 . . . weakened line-   26 . . . end ribbon section-   28 . . . major ribbon section-   30 . . . extension part-   32 . . . tab-   34 . . . joint portion-   36 . . . penetrating slit-   38,40 . . . hook

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the present invention will be described inmore detail with reference to the attached drawings wherein commonreference numerals are used for designating the corresponding componentsthroughout the drawings.

FIG. 1 is a partially sectional front view of a cold-shrink tube device10 according to one embodiment of the present invention; FIG. 2 is anenlarged front view of a core member 12 according to the one embodimentof the present invention; and FIGS. 3 and 4 are views illustrating astate of the core member 12 after being molded. The cold-shrink tubedevice 10 has a shape of a linear tube having two open ends and can beused as a cold-shrink type covering tube for protecting a linearconnected portion of a cable (a covered electric wire), for example.However, the use of the cold-shrink tube device should not be limitedthereto.

The cold-shrink tube device 10 includes a hollow cylindrical elastictube member 16 having open ends at longitudinal opposite ends thereofand a pair of hollow tubular core members 12 removably disposed withinend regions 18 of the interior of the elastic tube member 16, eachhaving a predetermined length from the respective open end 14, so thatthe end region 18 is maintained in an elastically expanded state. Theelastic tube member 16 has an intermediate region 20 integrallyconnected to the opposite end regions 18 in a coaxial manner, wherein aninner diameter of the respective end region 18 in an unloaded statewithout the core member 12 disposed therein is smaller than an innerdiameter of the intermediate region 20 in an unloaded state.Accordingly, when the cold-shrink tube device 10 is mounted to theobjective (for example, an electric wire connected portion) whileremoving the core members 12 therefrom, the opposite end regions 18 ofthe elastic tube member 16 are brought into tight contact with the outercircumference of the objective under the elastic recovery force thereofand the intermediate region 20 covers the aimed portion of theobjective.

The elastic tube member 16 is formed of an elastomer inherently havingan electric insulation property and flexibility to have the opposite endregions 18 and the intermediate region 20, which regions are preferablyintegrally made of the same material by an injection molding process. Asmaterials favorably used for the elastic tube member 16 are, forexample, ethylene-propylene rubber (particularly EPDM), chloroprenerubber, butyl rubber, silicone rubber, natural rubber, fluororubber andsilicone-modified EPDM. Particularly, when the cold-shrink tube device10 is used as a covering tube for the connected portion of the electricwire, at least opposite end regions 18 of the elastic tube member 16preferably has an elongation set of 40% or less, more preferably 15% orless, measured in accordance with JIS:K6301 (100° C., 22 hours) (seeJapanese unexamined Patent Publication (Kokai) No. 7-57798).

The respective core member 12 includes a hollow tubular cylindrical body22 and disposed in the end region 18 so that a central axis 22 a of thebody 22 is aligned with a central axis 16a of the elastic tube member16. The respective core member 12 has an inner diameter sufficientlylarger than an outer diameter of the objective (for example, a connectedportion of electric wire) to which the cold-shrink tube device 10 isapplied as well as a rigidity capable of maintaining the end region 18of the elastic tube member 16 in an elastically expanded state having apredetermined diameter against the elastic recovery force thereof. Aweakened line 24 continuously extending over the entire axial length ofthe body 22 in a spiral manner is formed in the respective core member12. The body 22 can be torn in a ribbon shape along the weakened line 24from one axial end 22 b thereof as a tearing-start end.

The weakened line 24 is formed in the body 22 of the core member 12 sothat a distance between every adjacent coils (an axial distance of thebody 22) becomes uneven. That is, a ribbon-like region formed in aspiral manner in the body 22 by the weakened line 24 has an end ribbonsection 26 defined between the weakened line 24 adjacent to thetearing-start end 24 and the one axial end 22 b of the body 22 and amajor ribbon section 28 having an axial dimension larger than that ofthe end ribbon section 26. The major ribbon section 28 is a sectionmainly maintaining the elastically expanded state of the end region 18of the elastic tube member 16 among the ribbon-like regions of the body22. In this definition, a dimension occupied by the major ribbon section28 relative to all the ribbon-like regions in the body 22 can bedetermined in correspondence to the axial direction of the end region18.

In the embodiment illustrated, when the core member 12 is properlyarranged in the end region 18 of the elastic tube member 16, theribbon-like region with about three coils including the end ribbonsection 26 and the major ribbon section 28 is accommodated inside theend region 18. In this regard, an axial dimension of the end ribbonsection 26 may be approximately 80% of the axial dimension of the majorribbon section 28 or less.

The core member 12 further includes an extension part 30 integrallyconnected to the end ribbon section 26 and extending from the body 22.At a distal end of the extension part 30, a substantially annular tab 32is integrally formed. The extension part 30 passes through the insidespace of the body 22 and a distal end tab 32 thereof projects outsidefrom the other axial end 22 c of the body 22. In this state, the coremember 12 is disposed in the end region 18 of the elastic tube member 16so that the other axial end 22 c of the body 22 and the tab 32 a of theextension part 30 are exposed from the open ends 14 of the elastic tubemember 16.

The core member 12 is integrally molded with resinous material such ashard plastic preferably by an injection molding process. In this case,for the purpose of facilitating the manufacture of mold, as shown inFIGS. 3 and 4, the extension part 30 is advantageously formed integrallywith the body 22 via an extension part 24′ of the weakened line 24except for a small section adjacent to the distal end tab 32. In theillustrated embodiment, the extension part 30 is molded to havesubstantially the same widthwise dimension as the axial dimension (thatis, a widthwise dimension) of the end ribbon section 26 and a lengthcorresponding to approximately one coil of the ribbon-like region formedin the body 22. And, after the core member 12 has been molded and priorto being disposed inside the end region 18 of the elastic tube member16, the extension part 30 is torn along the extended section 24′ of theweakened line 24 from the end ribbon section 26 of the body 22 andinserted into the inside space of the body 22. In this regard, asmaterials favorably used for the core member 12 are, for example,cellulose acetate, cellulose butyrate, polypropylene, polyethylene andpolyvinyl chloride.

According to the core member 12 of the above structure, it is possibleto make the axial dimension (that is, the widthwise dimension) of themajor ribbon section 28 in the ribbon-like region formed in the body bythe weakened line 24 to be sufficiently larger than that of the endribbon section 26 by properly adjusting the axial distance between theadjacent coils of the weakened line 24 extending in a spiral manner,while it is possible to reduce the widthwise dimension of the extensionpart 30 inserted into the inside space of the body 22 in correspondenceto the widthwise dimension of the end ribbon region 26. Thus, accordingto the core member 12, since a total length of the ribbon-like piecetorn from the body 22 becomes shorter, it is possible to decrease thedegree of entanglement of the ribbon-like piece with the objective.Also, since the inside space of the body 22 can be sufficiently due tothe reduction of the width of the extension part 30, it is possible tosmoothly insert the objective into the cold-shrink tube device 10.

Also, since the body 22 is cylindrical from the first in the core member12 molded as an integrally molded product, it is unnecessary to increasethe mechanical strength of the weakened line 24 even if the widthwisedimension of the major ribbon section 28 increases. In addition, sincethe weakened line 24 is easily stabilized in structure, it is possibleto realize the stable and smooth tearing operation less in variation ofthe tearing force. Further, since the distal end 32 of the extensionpart 30 is integrally moldable to have a desired configuration by aninjection molding process, it is possible to simplify the manufacturingprocess.

There may be cases wherein the core member 12 is removed by using aremote handling tool for the purpose of preventing the electric shockfrom occurring when the cold-shrink tube device 10 having theabove-mentioned core member 12 is applied, for example, to the connectedportion of the electric wire. In such cases, it is possible to quicklyremove the core member 12 from the elastic tube member 16 while avoidingthe entanglement of the ribbon-like piece torn from the body 22 aroundthe connected portion of the electric wire by linearly pulling theextension part 30 due to the simple linear motion or rotation of theremote handling tool gripping the tab 30 of the extension part 30 of thecore member 12. At this time, since the ribbon-like piece spirally tornfrom the body 22 has a configuration in which a stress concentrationhardly occurs, a risk of severance of the ribbon-like piece becomessmaller even though the extension part 30 is vigorously pulled.

In the core member 12 formed as an integrally molded product, theweakened line 24 may be formed as a perforated line having a pluralityof joint portions 34 and a plurality of penetrating slits 36 arrangedalternately with each other. According to such a weakened line 24, thetearing force for tearing the body 22 into a ribbon-like piece may beproperly adjustable by selecting the dimension and the number of theplurality of joint portions 34. A preferable tearing force for the body22 is, for example, in a range from approximately 20 Newtons (N) toapproximately 40 N (from approximately 2 kgf to approximately 4 kgf).

The force necessary for tearing the body 22 of the core member 12 can beadjusted by selecting shapes of the respective joint portions 34 in theweakened line 24. In view of this standpoint, as shown in FIG. 5, therespective joint portion 34 is preferably has a pair of outer surfaces34 a, 34 b intersecting at an acute angle each other on the tearingstart side (the tearing direction is indicated by an arrow a). Theintersecting angle of the outer surfaces 34 a, 34 b in the respectivejoint portion 34 may be suitably selected provided the above-mentionedtearing force is obtained; for example, 45 degrees or less. In thisregard, the plurality of joint portions 34 in the weakened line 24preferably have the same dimension and shape because the variation ofthe tearing force during the tearing operation is suppressed.

According to the cold-shrink tube device 10, in the core member 12disposed in the end region 18 of the elastic tube member 16, the endribbon section 26 of the body 22 tends to flex inward in the diametricaldirection because it is pressed by a tapered region at a boundarybetween an expanded area (or an end region 18) and a non-expanded area(or an intermediate region 20). This pressure may cause the breakage ofthe weakened line 24 at a tearing start end 24 a, and there is a risk inthat the unintentional breakage of the weakened line 24 increases withtime. To avoid such a risk, as shown in FIG. 2, one joint portion 34′ ispreferably formed at the tearing start end 24 a of the weakened line 24so that this joint portion 34′ has a tearing strength higher than theother joint portions 34.

To simply and effectively increase the tearing strength of the jointportion 34′ at the tearing-start end 24 a of the weakened line 24, thecross-sectional area of the joint portion 34′ is preferably larger thanthat of the other joint portion 34, for example, in FIG. 5. Also, it ispossible to increase the tearing strength of the joint portion 34′ bymaking an intersecting angle between the outer surfaces 34 a and 34 b inthe joint portion 34′ to be larger than the intersecting angle in theother joint portion 34. To achieve the above-mentioned object, thetearing strength of the joint portion 34′ at the tearing-start end 24 aof the weakened line 24 is, for example, 1.5 to 2 times the tearingstrength of the other joint portion 34 (that is, the tearing force ofthe body 22), and therefore the shape of the joint portion 34′ should beselected to have such a tearing force. Further, if necessary, 1 toseveral number of the joint portions 34 (preferably 1 to 3) located inthe vicinity of the joint portion 34′ rearward therefrom as seen in theextending direction; i.e., in the tearing direction of the weakened line24 may have the tearing strength larger than that of the other jointportion 34 in a similar manner.

Cross-sectional shapes of the respective joint portions 34, 34′ are notlimited to an equilateral triangle as shown in FIG. 5, but may beselected from various cross-sectional shapes as shown in FIGS. 6(a) to6(e). In either shape, the joint portion 34 has a pair of outer surfaces34 a, 34 b intersected at an acute angle on the tearing-start side.

To further smoothly insert the objective to be mounted into thecold-shrink tube device 10, the core member 12 preferably has anengaging mechanism for temporarily anchoring the extension part 30 inthe other axial end region of the body 22. This engaging mechanism maybe a hook 38 projected outward at an intermediate position in theextension part 30. The hook 38 is preferably integrally molded with theextension part 30. The extension part 30 is held at a position close tothe inner surface of the body 22 by detachably engaging the hook 39 witha portion adjacent to the other axial end 22 c, whereby a sufficientinside space is guaranteed in the body 22.

Or, as shown in FIG. 8, a hook 40 engaging mechanism may be integrallyprojected from a desired position on the inner surface adjacent to theother axial end 22 c of the body 22. Also, as shown in FIG. 9, theengaging mechanism may be formed so that no joint portion 34 is providedat a tearing-finish end 24 b of the weakened line 24 in the other axialend 22 c of the body 22 and the extension part 30 is detachably insertedinto the penetrating slit 36 adjacent to the tearing-furnish end 24 b.

The present invention has been described above with reference to thepreferred embodiments. However, the present invention should not belimited thereto but may be variously modified and varied within thedefinition of a scope of claim for patent. For example, in the coremember of the integrally molded product, the ribbon-like area formed ina spiral form by the weakened line has a uniform axial dimension as awhole, while the extension part integrally connected to the ribbon-likearea at one axial end of the body may has a widthwise dimension smallerthan that of the axial dimension of the ribbon-like area. It will beunderstood that the same operation and effect are obtainable as those ofthe core member 12 described above.

The structure of the core member according to the present invention maybe applied to a cold-shrink tube device having a core member over theentire length of an elastic tube member. Of course, the presentinvention is applicable to a cold-shrink tube device of a bifurcatetype. Further, the present invention is applicable to a cold-shrink tubedevice having a hollow inner layer element of an elastomer different incharacteristic fixedly disposed in the end region for the purpose ofimproving the sealing ability in the end region of the elastic tubemember (see Japanese Unexamined Patent Publication (Kokai) No.10-42447).

EXAMPLE

The core member 12 shown in FIG. 2 was integrally formed by an injectionmolding process, so that the axial dimension of the end ribbon region 26of the body 22 is 7 mm, the axial dimension of the major ribbon regionis 10 mm, the axial dimension of the ribbon region between the bothgradually increases from 7 mm to 10 mm and the inner diameter of thebody 22 is 34.8 mm. A plurality of joint portions 34 in the weakenedline 24 were formed so that a cross-sectional area of the joint portion34′ at the tearing-start end 24 a is 0.4 mm² and those of the otherjoint portions 34 are 0.3 mm². According to this arrangement, thetearing force necessary for tearing the body 22 in a ribbon-like piecewas approximately 60 N (approximately 6 kgf) at the start of tearing andapproximately 40 N (approximately 4 kgf) during the tearing of all theresidual portion.

This core member 12 was disposed within the elastic tube member 16having the end region 18 of approximately 30 mm axial dimension toprepare the cold-shrink tube device 10 shown in FIG. 10. In theoperation for mounting this cold-shrink tube device 10 to the electricwire connected portion, the workability of the tearing operation of thecore member 12 was studied, by linearly pulling tab 32 of the extensionpart 30 generally in the axial direction while changing the number ofcoils in the ribbon-like area of the core member 12 located in the endregion. In the experiment, the tearing operation was repeated ten timeon the respective number of coils by using the remote handling tool.Results are shown in the following table. TABLE 1 Workability fortearing core member (number) Number of coils in the Slightly Impossibleto end region of ribbon Easily removed entangled remove Less than 2.5 100 0 2.5 to 3.0 (less than 3.0) 6 4 0 3.0 to 3.5 (less than 3.5) 2 5 33.5 to 4.0 (less than 4.0) 0 3 7

As shown in the above table, in the cold-shrink tube device 10, it wasfound that the number of coils in the ribbon-like area of the coremember 12 located in the end region 18 of the elastic tube member 16 ispreferably less than about three for the purpose of mitigating theentanglement of the core member 12 with the objective.

As apparent from the above description, according to the presentinvention, in the cold-shrink tube device having a tearable core member,it is possible to quickly and correctly remove the core member from theelastic tube member without deteriorating the mounting workability tothe objective. Also, there is no risk in that the ribbon-like piece tornfrom the core member body is entangled with the objective of thecold-shrink tube device or cut during the tearing operation, whereby thestable tearing operation is realized.

1. A core member comprising a hollow tubular body and a weakened lineformed to extend spirally and continuously over an entire axial lengthof said body, said body being able to be torn into a ribbon shape alongsaid weakened line from an end of said weakened line provided as atearing-start end at one axial end of said body, characterized in that:said weakened line comprises a perforated line including a plurality ofjoint portions and a plurality of penetrating slits arrangedalternately, and extends in a spiral with uneven gaps defined betweenadjacent coils in an axial direction of said body; and that a region ofsaid ribbon shape, defined in a spiral on said body by said weakenedline, includes an end ribbon section defined, adjacent to saidtearing-start end, between said weakened line and said one axial end ofsaid body, and a major ribbon section having an axial dimension largerthan an axial dimension of said end ribbon section.
 2. A core member asset forth in claim 1, wherein one of said joint portions is formed atsaid tearing-start end of said weakened line having a tearing strengthlarger than that of remaining joint portions.
 3. A core member as setforth in claim 2 wherein several joint portions near said one jointportion at said tearing-start end of said weakened line also have a tearstrength larger than that of remaining joint portions.
 4. A core memberas set forth in claim 1, wherein each of said joint portions of saidweakened line includes a pair of outer surfaces mutually crossing in anacute angle at a tearing-start side of each joint portion.
 5. A coremember as set forth in any claims 1, further comprising an extensionpart connected integrally with said end ribbon section and extendingfrom said body, a substantially annular tab being integrally formed at adistal end of said extension part, wherein said body, said extensionpart and said tab are formed as a one-piece article molded from aresinous material.
 6. A core member as set forth in claim 1, furthercomprising an engaging mechanism for temporarily anchoring saidextension part on another axial end region of said body.
 7. A coremember comprising a hollow tubular body and a weakened line formed toextend spirally and continuously over an entire axial length of saidbody, said body being able to be torn into a ribbon shape along saidweakened line from an end of said weakened line provided as atearing-start end at one axial end of said body, characterized in that:said core member comprises an extension part connected integrally with aregion of said ribbon shape, defined in a spiral on said body by saidweakened line, at said one axial end of said body; and that saidextension part includes a width dimension smaller than an axialdimension of said region of said ribbon shape.
 8. A cold-shrink tubedevice comprising an elastic tube member including an opening end, and ahollow tubular core member removably arranged inside said elastic tubemember in a region of a predetermined length from said opening end tohold said region in an elastically expanded condition, characterized inthat: said hollow tubular core member comprises a core member as setforth in any one of claims 1 or 7.